A problem often encountered in the surface mount electronics industry is that of accurately screen printing solder paste, conductive epoxies, and other materials onto printed circuit boards. This is typically done by placing an image stencil over the board, and then spreading viscous material (e.g., solder paste) over the surface of the stencil, forcing it through the stencil apertures and onto the circuit board below. The level of detail that can be produced by this process is controlled in part by the quality of the tool used to spread the material onto the stencil. The most common tool currently used for this purpose is a metal-bladed squeegee.
Conventional squeegee blades are typically made of carbon steel, stainless steel, or nickel. The life of carbon steel blades can be significantly shortened by corrosion in the aggressive environment of a solder paste printing system. Both types of steel can cause significant wear to stencils used for screen printing, resulting in high retooling costs when stencils are frequently replaced. Further, it can be relatively difficult to clean excess solder paste off of these types of blades after printing. Nickel plating or the use of nickel blades has been found to alleviate these problems somewhat by reducing the coefficient of friction of the squeegee blade, but corrosion, wear of blades and stencils, and cleaning difficulties are still obstacles to inexpensive, high-quality screen printing of solder pastes, conductive epoxies, and the like.